Go to Youtube and search for nearly any popular song, and after the first few instances of the official video, and the artist doing a live version or whatever, you start to see "Youtube covers."
It's such a modern-day convention. A person who plays acoustic guitar or piano or whatever, who sets up a camera in their room, and records and uploads a video of themselves doing their favorite song, acoustically.
People have a lot of fun turning big pop hits (like Gnarls Barkley's "Crazy" or Britney Spears "Oops I Did It Again") into strummy ballads. And it's propelled a few folks to some mini-online-fame.
But it's only natural that this fun exercise shouldn't just be the province of amateurs. So occasionally you'll find people like Ben Folds busting something out on the web.
One of my favorite sources is Julian Velard, who is a great combination of super talented and super hilarious.
He's made great use of the web, frequently uploading originals and covers and concert snippets and offhanded comments. It's a great release of creativity.
Enjoy this one. I like it because, despite the initial suggestion that it will be super-goofy, I think that deep-down, Julian sincerely loves this Wham classic.
Hear the song on Youtube.